Rainbow of Light to Image Blood Cells

This optical instrument, no bigger than a breadbox, is able to provide high-resolution images of blood coursing through our veins without the need for harsh and short-lived fluorescent dyes.

"We have invented a new optical microscope that can see individual blood cells as they flow inside our body," says Lior Golan of the Israel Institute of Technology. By eliminating a long wait-time for blood test results, the new microscope might help spotlight warning signs, like high white blood cell count, before a patient develops severe medical problems. The portability of the device could also enable doctors in rural areas without easy access to medical labs to screen large populations for common blood disorders, Golan notes.

Using the new microscope, the researchers imaged the blood flowing through a vessel in the lower lip of a volunteer. They successfully measured the average diameter of the red and white blood cells and also calculated the percent volume of the different cell types, a key measurement for many medical diagnoses.

The device relies on a technique called spectrally encoded confocal microscopy (SECM), which creates images by splitting a light beam into its constituent colours. The colours are spread out in a line from red to violet. To scan blood cells in motion, a probe is pressed against the skin of a patient and the rainbow-like line of light is directed across a blood vessel near the surface of the skin. As blood cells cross the line they scatter light, which is collected and analysed. The colour of the scattered light carries spatial information, and computer programs interpret the signal over time to create 2-D images of the blood cells.

Currently, other blood-scanning systems with cellular resolution do exist, but they are far less practical, relying on bulky equipment or potentially harmful fluorescent dyes that must be injected into the bloodstream.

"An important feature of the technique is its reliance on reflected light from the flowing cells to form their images, thus avoiding the use of fluorescent dyes that could be toxic," Golan says. "Since the blood cells are in constant motion, their appearance is distinctively different from the static tissue surrounding them." The team's technique also takes advantage of the one-way flow of cells to create a compact probe that can quickly image large numbers of cells while remaining stationary against the skin.